Pointing devices allow users to move a curser or other indicators on a computer display in response to the user's movement. A normal computer mouse pointing device converts horizontal movement over a planar surface in two dimensions into corresponding curser movement on a computer screen. The mouse includes a sensor that is typically a laser or roller ball sensor that detects movement over a surface.
Other types of pointing devices have been designed which operate in three dimensional space and do not require the detection of movement over a surface. Motion detecting mechanisms include gyroscopes that detect rotational movement of the pointing device and accelerometers that detect linear movement. The gyroscopes and accelerometers emit signals that correspond to the movements of the pointing device and are used to control the movement of a cursor on the computer screen. Examples of hand-held angle-sensing controller are described in U.S. Pat. No. 5,898,421, titled GYROSCOPIC POINTER AND METHOD, issued to Thomas J. Quinn on Apr. 27, 1999, and U.S. Pat. No. 5,440,326, titled GYROSCOPIC POINTER, issued to Thomas J. Quinn on Aug. 8, 1995. A problem with existing three dimensional pointing devices is that if the user naturally holds the device at an angle offset from horizontal, the movement of the pointing device results in a cursor movement that is offset by roll angle, i.e., horizontal movement of the pointing device held at a roll angle results in angled movement of the cursor on the computer screen.
Some pointing devices are able to provide roll compensation for the natural hand position of the user. However, a problem with existing roll compensated pointing devices is that they utilize a very complex trigonometric matrix algorithm which requires high powered processors that draw a significant amount of electrical power and are more expensive. For cheap or low power processing units, the trigonometric form slows the process of computation, making it difficult to operate with real time computation constraints. Since the pointing device is preferably a cordless device, the portable batteries used to operate the more powerful processor may require frequent recharging or replacement.
What is needed is an improved pointing device that performs roll compensation in a more energy efficient manner so that an inexpensive low powered processor can be used and battery live can be substantially improved.